1. Field of the Invention
The present invention relates to a motorcycle having an exhaust chamber arranged above an engine with an air guide plate for separating the exhaust chamber from the motorcycle engine carburetor and for guiding the air flow from the motorcycle radiator to the rear of the motorcycle. Further, the present invention relates to a motorcycle having an air guide duct for carrying air from the radiator to the rear of the motorcycle to improve the air resistance of the motorcycle.
2. Description of the Prior Art
In motorcycles having an exhaust chamber located above the engine and a fuel tank located below the engine, it is necessary to provide a shield for the heat of the exhaust chamber and to cool down the same, because a rider receives substantial heat from the exhaust chamber as compared to a motorcycle having the exhaust chamber located below the engine.
In a motorcycle having a water-cooled engine and a carburetor arranged behind the radiator, it is necessary to prevent the hot air, which has passed through the radiator, from flowing into the carburetor because the hot air will heat the carburetor and is sucked in by the carburetor.
Further, it is well known that the air resistance of a motorcycle body has large influences upon the running performance of the motorcycle. In a motorcycle which frequently runs at a high speed, such as a motorcycle for road races, it is necessary to lower the air resistance by such means as cowlings attached to the front and rear of the motorcycle body the cowlings being molded to have smooth outer surfaces.
FIG. 1 shows a conventional example of a road race motorcycle which is equipped with cowlings in the front and at the rear of the body so as to reduce the air resistance. This motorcycle is of the water-cooled type, in which a radiator 3 and an engine 4 are mounted between a front wheel 1 and a rear wheel 2. A fuel tank 5 is located above the engine 4, and an exhaust pipe 6 extends below the engine 4 to the rear of the motorcycle body. The front portion of the body, including the engine 4 and the radiator 3, is covered with a front cowling (which is referred to as a "front cowl") 7, and the rear of the fuel tank 5 is covered with a seat cowling (which is referred to as a "seat cowl") having a seat portion 9a on which is seated a rider 8. The air resistance is reduced by the two cowlings 7 and 9.
The front cowl 7 has its side rear edges 7a extending to the vicinity of the front ends of the legs 8a of the rider 8, to cover the sides of the engine 4 and to have a width slightly larger than that between the two legs 8a of the rider 8. The seat cowl 9 is preferably narrow so as to facilitate the shift of the weight of the rider 8 to thereby improve riding stability and is usually made narrower than the width of the rider 8. If the seat cowl 9 is made narrower than the rider 8, however, as shown in FIG. 2, steps (.lambda.) are formed at the back of the legs 8a of the rider 8 whereby boundary layers (.quadrature.) of the air flow laminated at the sides of the front cowl 7 are separated at the rear of the legs 8a to establish vortexes behind of the legs 8a which can cuase air resistance.
In the motorcycle of the prior art, moreover, the flow directions of the slip streams (i.e., the air flow having passed through the radiator 3) of the radiator 3 are not especially controlled but are merely discharged in a natural manner from clearances between the front cowl 7 and the engine 4. In this discharging method, however, the slip streams of the radiator 3 impinge upon the engine 4, as shown in FIG. 2, so that the flow of the slip streams in the front cowl 7 become turbulent thereby increasing air resistance.